Heat transfer in a twin-screw multiphase pump: Thermal modeling and one application in the petroleum industry

This paper presents a model of the heat transfer processes in the casing and rotors of a twin-screw multiphase pump. The model was developed to study the influence of temperature rise in the subsea multiphase pumping system-500 (SMPS), being developed by Petrobras, that operates with a twin-screw multiphase pump. The model is divided in three parts: heat transfer in the casing, in the rotor and energy balance of fluid. For the rotor, a helicoidal coordinate system is used to calculate the heat transfer. Axial symmetry is considered so it is possible to construct a two-dimensional model. The casing is modeled using an eccentric cylindrical coordinate system. In this case, the temperature gradient in axial direction is neglected and a two-dimensional calculation is carried out. The finite volume method is used to solve the transformed partial differential equations. With the two heat transfer models implemented, the fluid temperature is calculated using a simple energy balance that takes into account electric power, transferred heat and fluid internal energy. The implemented model was used to simulate thermal behavior of casing and rotors during loss of prime events faced by SMPS-500. Experimental data collected in pump trials are used as initial input parameters and the model calculates temperature evolution during the loss of prime events.